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<script>
    //   JSON字符串 
    // let str = '{"username":"zs"}'
    // let o = JSON.parse(str)
    // 通过try-catch来告诉浏览器，自己处理错误
    try {
        let str = '{"username":"zs"}'
        let o = JSON.parse(str)
    }catch{
        console.log(123)
    }

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